Method and system for virtualizing flow tables in a software-defined networking (sdn) system

ABSTRACT

In one embodiment, a method is implemented in a network element coupled to the SDN system, which contains a set of network elements processing traffic flows and a SDN controller managing the set of network elements. The method includes creating a set of virtual tables for processing packets of traffic flows at the network element based on a set of flow tables of the network element, where the set of flow tables is ordered in a sequence. The method further includes mapping each of the set of virtual tables to a single flow table of the set of flow tables, where the mapping causes at least one flow table being mapped to a plurality of the set of virtual tables. The method also includes forwarding packets of traffic flows to the set of virtual tables for processing.

FIELD OF INVENTION

The embodiments of the invention are related to the field of networking.More specifically, the embodiments of the invention relate to a methodand system for virtualizing flow tables in a software-defined networking(SDN) system.

BACKGROUND

Software-Defined networking (SDN) is a network architecture that aims atdecoupling control plane functions from data plane functions such thatseparate apparatuses may be utilized for different functions. In the SDNarchitecture, network intelligence and states are logically centralized,and the underlying network infrastructure is abstracted from theapplications. As a result, networking may be simplified and newapplications become feasible. For example, network virtualization can beaccomplished by implementing it in a software application where thecontrol plane is separated from the data plane. Also, a networkadministrator of a SDN system may have programmable central control ofnetwork traffic without requiring physical access to the system'shardware devices. With these benefits, SDN architecture based systems(referred to as SDN systems or SDN networks exchangeably herein below)are gaining popularity among carriers and enterprises.

For implementing SDN, the Open Networking Foundation (ONF), anindustrial consortium focusing on commercializing SDN and its underlyingtechnologies, has defined a set of open commands, functions, andprotocols. The defined protocol suites are known as the OpenFlow (OF)protocol. In the OpenFlow protocol, packets of traffic flows areforwarded through one or more flow tables in an OpenFlow switch. Whenthere are a plurality of flow tables in an OpenFlow switch, the flowtables are sequentially numbered, starting at 0. The packets areprocessed through an Openflow flow table pipeline, starting at flowtable 0. The processed packets at a higher numbered flow table cannot belooped back to be processed again by the same flow table or a lowernumbered flow table. In addition, each flow table contains its own keycomposition for lookup, and the key compositions are configured a prioriby a SDN controller.

SUMMARY

A method for virtualizing flow tables in a software-defined networking(SDN) system is disclosed. The method is implemented in a networkelement coupled to the SDN system, which contains a set of networkelements processing traffic flows and a SDN controller managing the setof network elements. The method includes creating a set of virtualtables for processing packets of traffic flows at the network elementbased on a set of flow tables of the network element, where the set offlow tables is ordered in a sequence. The method further includesmapping each of the set of virtual tables to a single flow table of theset of flow tables, where the mapping causes at least one flow tablebeing mapped to a plurality of the set of virtual tables. The methodalso includes forwarding packets of traffic flows to the set of virtualtables for processing.

A network element configured to virtualize flow tables in asoftware-defined networking (SDN) system is disclosed. The networkelement is coupled to software-defined networking (SDN) system, whichcontains a set of network elements processing traffic flows and a SDNcontroller managing the set of network elements. The network elementcreates a set of virtual tables for processing packets of traffic flowsat the network element based on a set of flow tables of the networkelement, where the set of flow tables is ordered in a sequence; map eachof the set of virtual tables to a single flow table of the set of flowtables, where the mapping causes at least one flow table being mapped toa plurality of the set of virtual tables; and forward packets of trafficflows to the set of virtual tables for processing.

A non-transitory machine-readable medium for virtualizing flow tables ina software-defined networking (SDN) system is disclosed. When executedby a processor, the non-transitory machine-readable medium causes theprocessor to perform operations in a network element coupled to asoftware-defined networking (SDN) system, which contains a set ofnetwork elements processing traffic flows and a SDN controller managingthe set of network elements. The operations include creating a set ofvirtual tables for processing packets of traffic flows at the networkelement based on a set of flow tables of the network element, where theset of flow tables is ordered in a sequence. The operations furtherinclude mapping each of the set of virtual tables to a single flow tableof the set of flow tables, where the mapping causes at least one flowtable being mapped to a plurality of the set of virtual tables. Theoperations also include forwarding packets of traffic flows to the setof virtual tables for processing.

Embodiments of the invention aim at improving the efficiency of tablelookup for packet forwarding. Through the mapping of flow tables tovirtual tables, the packet processing is more flexible and it savesstorage space as it avoids the need of storing fields such match fieldsof the flow tables multiple times.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that differentreferences to “an” or “one” embodiment in this specification are notnecessarily to the same embodiment, and such references mean at leastone. Further, when a particular feature, structure, or characteristic isdescribed in connection with an embodiment, it is submitted that it iswithin the knowledge of one skilled in the art to affect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described.

FIG. 1A illustrates an architecture of virtualizing SDN flow tablesaccording to one embodiment of the invention.

FIG. 1B illustrates separation of the virtual table and flow tableaccording to one embodiment of the invention.

FIG. 2 illustrates operations with virtualized flow tables according toone embodiment of the invention.

FIG. 3 is a flow diagram illustrating implementation of flow tablevirtualization according to one embodiment of the invention.

FIG. 4 is a flow diagram illustrating the operations of processing thepackets according to one embodiment of the invention.

FIG. 5A illustrates connectivity between network devices (NDs) within anexemplary network, as well as three exemplary implementations of theNDs, according to some embodiments of the invention.

FIG. 5B illustrates an exemplary way to implement the special-purposenetwork device 502 according to some embodiments of the invention.

FIG. 5C illustrates various exemplary ways in which virtual networkelements (VNEs) may be coupled according to some embodiments of theinvention.

FIG. 5D illustrates a network with a single network element (NE) on eachof the NDs of FIG. 5A, and a centralized approach for maintainingreachability and forwarding information (also called network control),according to some embodiments of the invention.

FIG. 5E illustrates the simple case of where each of the NDs 500A-Himplements a single NE 570A-H (see FIG. 5D), but the centralized controlplane 576 has abstracted multiple of the NEs in different NDs (the NEs570A-C and G-H) into (to represent) a single NE 570I in one of thevirtual network(s) 592 of FIG. 5D, according to some embodiments of theinvention.

FIG. 5F illustrates a case where multiple VNEs (VNE 570A.1 and VNE570H.1) are implemented on different NDs (ND 500A and ND 500H) and arecoupled to each other, and where the centralized control plane 576 hasabstracted these multiple VNEs such that they appear as a single VNE570T within one of the virtual networks 592 of FIG. 5D, according tosome embodiments of the invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knowncircuits, structures and techniques have not been shown in detail inorder not to obscure the understanding of this description. It will beappreciated, however, by one skilled in the art that the invention maybe practiced without such specific details. Those of ordinary skill inthe art, with the included descriptions, will be able to implementappropriate functionality without undue experimentation.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.“Coupled” is used to indicate that two or more elements, which may ormay not be in direct physical or electrical contact with each other,co-operate or interact with each other. “Connected” is used to indicatethe establishment of communication between two or more elements that arecoupled with each other. A “set,” as used herein refers to any positivewhole number of items including one item.

An electronic device (e.g., an end station, a network device) stores andtransmits (internally and/or with other electronic devices over anetwork) code (composed of software instructions) and data usingmachine-readable media, such as non-transitory machine-readable media(e.g., machine-readable storage media such as magnetic disks; opticaldisks; read only memory; flash memory devices; phase change memory) andtransitory machine-readable transmission media (e.g., electrical,optical, acoustical or other form of propagated signals—such as carrierwaves, infrared signals). In addition, such electronic devices includehardware, such as a set of one or more processors coupled to one or moreother components—e.g., one or more non-transitory machine-readablestorage media (to store code and/or data) and network connections (totransmit code and/or data using propagating signals), as well as userinput/output devices (e.g., a keyboard, a touchscreen, and/or a display)in some cases. The coupling of the set of processors and othercomponents is typically through one or more interconnects within theelectronic devices (e.g., busses and possibly bridges). Thus, anon-transitory machine-readable medium of a given electronic devicetypically stores instructions for execution on one or more processors ofthat electronic device. One or more parts of an embodiment of theinvention may be implemented using different combinations of software,firmware, and/or hardware.

A network device (ND) is an electronic device that communicativelyinterconnects other electronic devices on the network (e.g., othernetwork devices, end-user devices). Some network devices are “multipleservices network devices” that provide support for multiple networkingfunctions (e.g., routing, bridging, switching, Layer 2 aggregation,session border control, Quality of Service, and/or subscribermanagement), and/or provide support for multiple application services(e.g., data, voice, and video).

Scalability Issue of Forwarding Packets Through Flow Tables

According to the OpenFlow protocol, packets of traffic flow areprocessed through a set of ordered flow tables. The ordering of flowtables presents challenges in implementing some traditional applicationsin a SDN system complying with the OpenFlow protocol.

For example, in an Open Systems Interconnection (OSI) layer 2 (L2)application, the source media access control (MAC) learning anddestination MAC lookup for forwarding may be done on the same tablecalled MAC table or Bridge table according to the IEEE 802.1qtransparent bridging protocol. The table is used differently for thesource MAC learning and destination MAC lookup:

-   -   The key for the source MAC learning is the L2 domain identifier        (ID) and source MAC address of the L2 packet (i.e., an Ethernet        frame). If there is a match in the table (referred to as a        “hit”), nothing needs to be done; and if there is a lookup miss        (no matching entry in the table), the network element receiving        the L2 packet tries to learn the MAC address.    -   The key for the destination MAC lookup is the L2 domain ID and        destination MAC address of the L2 packet. If there is a match in        the table, the packet is forwarded per returned exit vector; and        if there is a lookup miss, the packet is sent to a flood list to        broadcast to all member of ports of the L2 domain.

Thus, for the transparent bridging application, the same table is usedfor the source MAC learning and destination MAC lookup for forwarding,and MAC aging is done on the same table. However, the keys for the twooperations are different, and the lookup miss operations are differenttoo. Note since a key may contain a set of one or more components, theterm “key component” is used to denote the component, a key componentmay be for an exact match to the match field(s) of the table, or onlyfor wildcard, or a mixed of exact/wildcard match.

If the same transparent bridging operations are implemented according tothe OpenFlow model, a possible implementation follows. Since the keysand operations following the lookup are different, two tables areneeded. Additionally, since the tables are sequentially numbered, assumethe two tables are Table X and Table Y, where X and Y are tableidentifiers (IDs), and X<Y. The operations in the two tables are thefollowing:

-   -   The source MAC learning table, Table X:        -   The key is the L2 domain ID and source MAC address;        -   If there is a hit—the packet may be forwarded to Table Y            (e.g., using a goto-table instruction);        -   If it is a miss—the packet is sent to the SDN controller for            source MAC learning and also forwarded to Table Y for            destination MAC lookup.    -   The destination MAC lookup table, Table Y:        -   The key is the L2 domain ID and destination MAC address;        -   If there is a hit, the packet is forwarded on;        -   If there is a miss—the packet is sent to the SDN controller            for flooding.

The Tables X and Y contain mostly same fields, yet they have to beduplicated as the lookup key components are different. In OpenFlow, eachflow table (referred to as an OpenFlow table) has preconfigured keycomponents, which are static in nature, and the SDN controller needs toconfigure the key components. In addition, the SDN controller needs toconfigure operations upon hit (through “instructions” field of a flowentry), and operations upon miss (through a table miss entry of thetable).

With duplication, the implementation is suboptimal. For example, in thetransparent bridging operations of an enterprise/core network setting,there often needs to be millions of table entries for each of the sourceMAC learning table and destination MAC lookup table. The duplicationcauses significant more storage overhead and uses much more processingresources in the network element (OpenFlow switch is one type of networkelement). When the table lookup is achieved through a costly searchengine such as a ternary content-addressable memory (TCAM) or longestprefix match (LPM) search engine, the cost for lookup is drasticallyincreased. In addition, despite the known duplication, the SDNcontroller needs to interact with both tables, and that causes moreprocessing resources at the SDN controller too. Furthermore, with thetwo tables contain many same entities, the synchronization between thetables presents a challenge to make the table consistent and correct.Thus, the implementation of L2 transparent bridging through the standardOpenFlow protocol may not scale well.

Not only L2 applications may encounter scalability issues inimplementing within the OpenFlow protocol, L3 applications may encountersimilar issues. For example, for L3 reverse path forwarding (RPF)filtering, the source IP address in L3 forwarding information base (FIB)needs to be looked up. Since the key components for lookup and the tablemiss handling likely are different, the source IP based RPF filteringand destination IP based packet forwarding use different flow tables,thus the FIB needs to be duplicated, which incurs the additional costsimilar to the L2 transparent bridging application.

While the two examples are given for implementing applications throughthe standard OpenFlow protocol, other applications may encounter similarissue with the duplication of flow tables and it is desirable to removethe duplication in implementing applications in a SDN system.

Architectures for Virtualizing Flow Tables

FIG. 1A illustrates an architecture of virtualizing SDN flow tablesaccording to one embodiment of the invention. System 100 is a SDN systemcontaining a network controller 104 (also referred interchangeably to asa SDN controller in this specification). The network controller 104manages a set of network elements, including a network element 102. Thedetailed operations of a network controller and network elements arediscussed herein below in relation to FIGS. 5A-F.

Flow tables store forwarding information to direct forwarding ofincoming packets by a network element. Flow tables are ordered in asequence that forms the processing pipeline for the incoming packets.The flow tables are numbered with flow table IDs, and each flow table IDis a unique numeric integer number. The flow tables are orderedaccording to the flow table IDs, and a flow table with a smaller flowtable ID is always at the front of a flow table with a bigger flow tableID in the processing pipeline. Thus, flow table 1 at reference 112 has asmaller flow table ID than that of flow table 2 at reference 114.

For a SDN system without implementing embodiments of the invention, thenetwork controller 104 configures the flow tables such as flow tables 1and 2, including match fields, key components for lookup, table misshandling, and statistics collection. When a packet is received andforwarded to a particular flow table such as flow table 1, the networkelement 102 searches for a matching entry in the flow table 1, and ifthe matching entry is found, the statistics is updated (e.g., through acounter), and the packet is processed through instructions correspondingto the matching entry, and metadata associated with the packet (e.g.,the output port, quality of service (Qos) indication) is also updated.If no matching entry is found, the packet is processed through a tablemiss handle entry.

According to one embodiment of the invention, a set of virtual tablesare created in the network element 102. The virtual tables are mapped tothe flow tables, and at least one flow table is mapped to a plurality ofvirtual tables. As illustrated, virtual tables 1 and 2 at references 162and 164 respectively map to flow table 1 at reference 112. Virtual table3 at reference 166 maps to flow table 2 at reference 114. Instead offorwarding packets based on flow tables, network element 102 forwardingpackets based on virtual tables referring to the mapping flow tables.

In one embodiment, the flow tables keep matching fields, which areshared by the virtual table(s) mapped to the flow tables, and thevirtual tables keep their respective key components, so that they mayuse their key components to do table lookup in the flow tables. Sincematching fields remain in the flow tables, the storage related tomatching fields are not duplicated, thus the virtualization results insaving versus the standard OpenFlow model.

FIG. 1B illustrates separation of the virtual table and flow tableaccording to one embodiment of the invention. Virtual table 1 atreference 162 maps to flow table 1 at reference 112. Flow table 1contains a number of flow entries such as flow entries 201-221. Eachflow entry in flow table 1 contains match fields and instructions field.

In one embodiment, the match fields in flow table 1 are same or similarto the match fields as defined in the OpenFlow protocol. They are to bematched against packets, and contain ingress ports, packet headers,other pipeline fields such as metadata specified by a previous flowtable. Flow table 1 may include a priority field (not shown) in eachflow entry, where the priority field is for matching precedence of theflow entry in one embodiment. Match fields (and optionally theadditional priority field) are used for the network element to match apacket against a flow entry. The matching is typically through a keythat contains a set of key components.

Flow table 1 also contain instructions fields that modify the action setor pipeline processing. While according to the OpenFlow protocol, theinstructions fields detail the action set to be taken to a packetmatching a particular flow entry, the zoom-in instructions 204illustrates that at least some instructions fields are different fromthe OpenFlow protocol standard. In instructions 204, each instructioncontains flow action(s) to be taken for a particular virtual tablethrough a tuple including a virtual table ID and flow action entity. Inother words, the flow action(s) taken to a packet is based on not onlythe matching flow entry in the flow table, but also the virtual tablemapped to the flow table. In one embodiment, not all the instructionscontain reference to virtual tables. For example, when a flow table ismapped to only a single virtual table, the reference to a virtual tableis not necessary.

The flow actions(s) to be taken for the particular virtual table are oneof the action sets as defined in the OpenFlow protocol in oneembodiment, including pop, push, quality of service actions, and goingto another flow table (Goto-Table).

Virtual table 1 includes virtual table mapping block 241, whichindicates which flow table the virtual table is mapped to. A virtualtable is mapped to a single flow table, and the virtual table mappingmay include a flow table ID indicating that the virtual table is mappedto the flow table. In an alternative embodiment, the virtual tablemapping is stored in network controller 104, which maps the virtualtable ID to the flow table ID.

Virtual table 1 also includes a key composition block 242, which is thekey containing the set of key compositions used to look up the matchfields of the corresponding flow table. Virtual table 1 includes a flowactions block 244, which contains a set of flow actions that may beperformed to a packet matching a flow entry of the corresponding flowtable. Virtual table 1 includes a counters block 246, which updates formatching packets. While the counters are maintained for each flow table,flow entry, port, queue, group, and etc. according to the OpenFlowprotocol, virtual tables maintain the counters (e.g., based on the flowactions at reference 244) in one embodiment of the invention. Inaddition, virtual table 1 includes a table miss handle 248 thatspecifies how to process packets unmatched by flow entries in thecorresponding flow table. Since one virtual table maps to a single flowtable, there is no ambiguity as of how the virtual tables are createdand maintained.

In one embodiment, the virtual table mapping block 241, the keycomposition block 242, the flow actions block 244, and table miss handleblock 248 are configured based on a request from the SDN controller. Thecounters blocks 246 are updated as packets processed through theprocessing pipeline.

Note that not every flow table is mapped to a virtual table in oneembodiment. For example, in some embodiment, some flow tables in theprocessing pipeline may be implemented without a significant amount ofduplication in table content, in that case, those flow tables may not bemapped to any virtual table, and they are implemented in a structureknown in the art, e.g, following the OpenFlow protocol.

The addition of virtual tables in the packet processing pipeline of anetwork element is advantageous in that matching fields is kept in theflow table while the operations to the packets matching the flow entryis performed according to the mapping virtual table. The matching fieldscan be long and take significant storage space. For example, accordingto the OpenFlow specification 1.3.0, the OpenFlow Extensible Match (OXM)format, each match field can be 259 bytes long. When performingoperations for applications such as L2 transparent bridging or L3 RPFfiltering, the matching fields are the same for multiple operations. Notduplicating the matching fields results in significant saving in storageand processing resources when there are millions of such match fields inthe applications such as L2 transparent bridging and L3 RPF filtering.With virtual tables being used to perform flow actions and multiplevirtual tables being mapped to a single flow table, the key componentsand table missing handles can still be predetermined by a networkcontroller, and the network controller can determine the respective keycomponents and table missing handles in the multiple virtual tables.Thus, the operations in the network controller require little or nomodification for the virtualization of flow tables.

Operations with Virtualized Flow Tables

FIG. 2 illustrates operations with virtualized flow tables according toone embodiment of the invention. Virtual table 1 and flow table 1 arethe same as the ones of FIG. 1B, and the same or similar referencesindicate elements or components having the same or similarfunctionalities. Task boxes 1 to 4 illustrate the order in whichoperations are performed according to one embodiment of the invention.

In one embodiment, packets are forwarded to the packet processingpipeline include both virtual tables and flow tables. The packets arefirst forwarded to a virtual table and they are then processed withreference to the corresponding flow table. After the process, thepackets are either forwarded to the next virtual table for furtherprocessing or to the network controller when the network elementrequires further input.

At task box 1, a packet is received at virtual table 1, and the networkelement directs the packet from the virtual table to its mapping flowtable to search for a matching flow entry. The mapping is based on apredetermined mapping between the virtual table and the flow table. Attask box 2, the network element searches the match fields of flowentries to find a matching flow entry. The searching is based on the keycomposition in virtual table 1. There may be multiple matching flowentries for a packet, in which case the flow entry with the higherpriority is selected as the matching flow entry.

Upon finding a matching flow entry, at task box 3A, the network elementdetermines a corresponding flow action in the matching flow entry. Theremay be multiple set of flow actions, each set for a particular virtualtable mapped to the flow table. Based on the virtual table that a packetbeing referred from (in this case virtual table 1), the set of flowactions for the virtual table is selected. In alternative, upon notfinding a matching flow entry, at task box 3B, the network elementperforms operations according to table miss handle 248.

At task box 4, the network element performs the set of flow actionsaccording to the selected flow actions selected at task box 3A. Inaddition, the counters may be updated based on the performance of theset of flow actions or the table miss handle.

Note that the packet processing pipeline according to the embodiments ofthe invention is different from the packet processing pipeline accordingto the existing OpenFlow such as the OpenFlow Switch SpecificationVersion 1.3.4 published on Mar. 27, 2014. The difference is mainly onthe network element (referred to as the OpenFlow switch) side. In orderto make the network element work according to the embodiments of theinvention, one or more ways may identify the network element with flowtable virtualization capability:

-   -   The network element may negotiate with the SDN controller and        indicate its virtualization capability.    -   A vendor extension may be added in communications between the        network element and the SDN controller so that the SDN        controller may recognize the vendor extension and know the        network element's virtualization capability.    -   A predetermined data path identifier is assigned for the network        element with flow table virtualization capability.    -   The network element may initiate communication through a        predetermined port to the SDN controller.

Once the table virtualization capability is identified by the SDNcontroller, the SDN controller may act accordingly, e.g., setting upmapping flow tables and virtual table and configures various fields andblocks in the flow tables and virtual tables.

Flow Diagrams for Implementing Flow Table Virtualization

FIG. 3 is a flow diagram illustrating implementation of flow tablevirtualization according to one embodiment of the invention. Method 300may be implemented in network element 102 of FIG. 1A according to oneembodiment of the invention.

At reference 302, a set of virtual tables is created for processingpackets of traffic flows. The creation is based on the set of flowtables of the network element. When the flow tables are created based onthe OpenFlow protocol, the flow tables are ordered in sequence. Thecreation of the set of virtual tables may be in response to a requestfrom a SDN controller managing the network element, and it may also betriggered by an operator of the SDN system that the network element is apart of.

In one embodiment, creating each virtual table includes performing atleast one of: setting a table identifier for the virtual table, settinga set of key components of the virtual table, setting a set of actionsupon receiving a matching packet, and setting an entry for matchingmiss.

At reference 304, each of the set of virtual tables is mapped to asingle flow table of the set of flow tables, where the mapping causes atleast one flow table being mapped to a plurality of the set of virtualtables. In one embodiment, the mapping each of the set of virtual tablescomprises mapping a table identifier of a virtual table to a tableidentifier of a flow table. The mapping may be based on a request fromthe SDN controller, and it may also be based on characteristics of thenetwork element.

At reference 306, packets of traffic flows are forwarded to the set ofvirtual tables for processing. The set of virtual tables process thepackets in coordination with the mapping flow tables. The set of virtualtables forms a processing pipeline of the network element, and theordered flow tables are referred to in processing the packets.

FIG. 4 is a flow diagram illustrating the operations of processing thepackets according to one embodiment of the invention. Method 400 may beimplemented in network element 102 of FIG. 1A according to oneembodiment of the invention. In one embodiment, method 400 is animplementation of reference 306.

At reference 402, upon receiving a packet of a traffic flow at a virtualtable, searching for a matching flow entry is performed in the mappingflow table of the virtual table. In one embodiment, the searching isperformed through matching key components of the packet to matchingfields of flow entries in its mapping flow table. The key components aredefined for the virtual table, and values of corresponding fields in thepacket are used for matching. For example, in L2 transparent bridgingoperation, the key components may be the L2 domain ID and source MACaddress, and these key components are the values of the L2 domain ID andsource MAC address fields in the header of the packet, and the keycomponents in the packet are referred to for the matching.

At reference 404, upon finding the matching flow entry in the mappingflow table, a corresponding set of actions of the matching flow entryfor the virtual table is determined The corresponding set of actions maybe one of the set of actions defined in the OpenFlow protocol in oneembodiment. At reference 406, the corresponding set of actions areperformed. Upon performing the corresponding set of actions, one or morecounters in the virtual table is updated at reference 408.

In alternative, upon finding no matching flow entry in the mapping flowtable, an instruction for match miss at the virtual table is performedat reference 410.

Upon finishing the processing of the packet, the packet may be sent tothe next virtual table or the SDN controller for further processing.Note the packet may be updated with revised or new metadata and changedpacket content. The packet update through the processing of the virtualtable may comply with the OpenFlow protocol according to one embodimentof the invention.

SDN and NFV Environment Utilizing Embodiments of the Invention

Embodiments of the invention may be utilized in a SDN and NFV networkcontaining network devices. A network device (ND) is an electronicdevice that communicatively interconnects other electronic devices onthe network (e.g., other network devices, end-user devices). Somenetwork devices are “multiple services network devices” that providesupport for multiple networking functions (e.g., routing, bridging,switching, Layer 2 aggregation, session border control, Quality ofService, and/or subscriber management), and/or provide support formultiple application services (e.g., data, voice, and video).

FIG. 5A illustrates connectivity between network devices (NDs) within anexemplary network, as well as three exemplary implementations of theNDs, according to some embodiments of the invention. FIG. 5A shows NDs500A-H, and their connectivity by way of lines between A-B, B-C, C-D,D-E, E-F, F-G, and A-G, as well as between H and each of A, C, D, and G.These NDs are physical devices, and the connectivity between these NDscan be wireless or wired (often referred to as a link). An additionalline extending from NDs 500A, E, and F illustrates that these NDs act asingress and egress points for the network (and thus, these NDs aresometimes referred to as edge NDs; while the other NDs may be calledcore NDs).

Two of the exemplary ND implementations in FIG. 5A are: 1) aspecial-purpose network device 502 that uses custom application-specificintegrated-circuits (ASICs) and a proprietary operating system (OS); and2) a general purpose network device 504 that uses common off-the-shelf(COTS) processors and a standard OS.

The special-purpose network device 502 includes networking hardware 510comprising compute resource(s) 512 (which typically include a set of oneor more processors), forwarding resource(s) 514 (which typically includeone or more ASICs and/or network processors), and physical networkinterfaces (NIs) 516 (sometimes called physical ports), as well asnon-transitory machine readable storage media 518 having stored thereinnetworking software, such as a virtual table coordinator (VTC) 555. Thevirtual table coordinator coordinates flow table virtualization asdiscussed herein above. A physical NI is hardware in a ND through whicha network connection (e.g., wirelessly through a wireless networkinterface controller (WNIC) or through plugging in a cable to a physicalport connected to a network interface controller (NIC)) is made, such asthose shown by the connectivity between NDs 500A-H. During operation,VTC 555 may be executed by the networking hardware 510 to instantiate aVTC instance (VI) 521, which performs methods as discussed herein abovein relation to FIGS. 1-4. VI 521 and that part of the networkinghardware 510 that executes that instance (be it hardware dedicated tothat networking software instance and/or time slices of hardwaretemporally shared by that networking software instance with others ofthe VTC instance 522), form a separate virtual network element 530A-R.Each of the virtual network element(s) (VNEs) 530A-R includes a controlcommunication and configuration module 532A-R (sometimes referred to asa local control module or control communication module) and forwardingtable(s) 534A-R, such that a given virtual network element (e.g., 530A)includes the control communication and configuration module (e.g.,532A), a set of one or more forwarding table(s) (e.g., 534A), and thatportion of the networking hardware 510 that executes the virtual networkelement (e.g., 530A). Note that the forwarding tables 534A-R containsboth flow tables and virtual table, and the flow table be structureddifferently from the flow tables known in the art. As illustrated inFIGS. 1B and 2, some fields and entries of the flow tables may beallocated in the corresponding virtual tables.

The special-purpose network device 502 is often physically and/orlogically considered to include: 1) a ND control plane 524 (sometimesreferred to as a control plane) comprising the compute resource(s) 512that execute the control communication and configuration module(s)532A-R; and 2) a ND forwarding plane 526 (sometimes referred to as aforwarding plane, a data plane, or a media plane) comprising theforwarding resource(s) 514 that utilize the forwarding table(s) 534A-Rand the physical NIs 516. By way of example, where the ND is a router(or is implementing routing functionality), the ND control plane 524(the compute resource(s) 512 executing the control communication andconfiguration module(s) 532A-R) is typically responsible forparticipating in controlling how data (e.g., packets) is to be routed(e.g., the next hop for the data and the outgoing physical NI for thatdata) and storing that routing information in the forwarding table(s)534A-R, and the ND forwarding plane 526 is responsible for receivingthat data on the physical NIs 516 and forwarding that data out theappropriate ones of the physical NIs 516 based on the forwardingtable(s) 534A-R.

FIG. 5B illustrates an exemplary way to implement the special-purposenetwork device 502 according to some embodiments of the invention. FIG.5B shows a special-purpose network device including cards 538 (typicallyhot pluggable). While in some embodiments the cards 538 are of two types(one or more that operate as the ND forwarding plane 526 (sometimescalled line cards), and one or more that operate to implement the NDcontrol plane 524 (sometimes called control cards)), alternativeembodiments may combine functionality onto a single card and/or includeadditional card types (e.g., one additional type of card is called aservice card, resource card, or multi-application card). A service cardcan provide specialized processing (e.g., Layer 4 to Layer 7 services(e.g., firewall, Internet Protocol Security (IPsec) (RFC 4301 and 4309),Secure Sockets Layer (SSL)/Transport Layer Security (TLS), IntrusionDetection System (IDS), peer-to-peer (P2P), Voice over IP (VoIP) SessionBorder Controller, Mobile Wireless Gateways (Gateway General PacketRadio Service (GPRS) Support Node (GGSN), Evolved Packet Core (EPC)Gateway)). By way of example, a service card may be used to terminateIPsec tunnels and execute the attendant authentication and encryptionalgorithms. These cards are coupled together through one or moreinterconnect mechanisms illustrated as backplane 536 (e.g., a first fullmesh coupling the line cards and a second full mesh coupling all of thecards).

Returning to FIG. 5A, The general purpose network device 504 includeshardware 540 comprising a set of one or more processor(s) 542 (which areoften COTS processors) and network interface controller(s) 544 (NICs;also known as network interface cards) (which include physical NIs 546),as well as non-transitory machine readable storage media 548 havingstored therein VTC 557. During operation, the processor(s) 542 executethe VTC 557 to instantiate a hypervisor 554 (sometimes referred to as avirtual machine monitor (VMM)) and one or more virtual machines 562A-Rthat are run by the hypervisor 554, which are collectively referred toas software instance(s) 552. A virtual machine is a softwareimplementation of a physical machine that runs programs as if they wereexecuting on a physical, non-virtualized machine; and applicationsgenerally do not know they are running on a virtual machine as opposedto running on a “bare metal” host electronic device, though some systemsprovide para-virtualization which allows an operating system orapplication to be aware of the presence of virtualization foroptimization purposes. Each of the virtual machines 562A-R, and thatpart of the hardware 540 that executes that virtual machine (be ithardware dedicated to that virtual machine and/or time slices ofhardware temporally shared by that virtual machine with others of thevirtual machine(s) 562A-R), forms a separate virtual network element(s)560A-R.

The virtual network element(s) 560A-R perform similar functionality tothe virtual network element(s) 530A-R. For instance, the hypervisor 554may present a virtual operating platform that appears like networkinghardware 510 to virtual machine 562A, and the virtual machine 562A maybe used to implement functionality similar to the control communicationand configuration module(s) 532A and forwarding table(s) 534A (thisvirtualization of the hardware 540 is sometimes referred to as networkfunction virtualization (NFV)). Thus, NFV may be used to consolidatemany network equipment types onto industry standard high volume serverhardware, physical switches, and physical storage, which could belocated in Data centers, NDs, and customer premise equipment (CPE).However, different embodiments of the invention may implement one ormore of the virtual machine(s) 562A-R differently. For example, whileembodiments of the invention are illustrated with each virtual machine562A-R corresponding to one VNE 560A-R, alternative embodiments mayimplement this correspondence at a finer level granularity (e.g., linecard virtual machines virtualize line cards, control card virtualmachine virtualize control cards, etc.); it should be understood thatthe techniques described herein with reference to a correspondence ofvirtual machines to VNEs also apply to embodiments where such a finerlevel of granularity is used.

In certain embodiments, the hypervisor 554 includes a virtual switchthat provides similar forwarding services as a physical Ethernet switch.Specifically, this virtual switch forwards traffic between virtualmachines and the NIC(s) 544, as well as optionally between the virtualmachines 562A-R; in addition, this virtual switch may enforce networkisolation between the VNEs 560A-R that by policy are not permitted tocommunicate with each other (e.g., by honoring virtual local areanetworks (VLANs)).

The third exemplary ND implementation in FIG. 5A is a hybrid networkdevice 506, which includes both custom ASICs/proprietary OS and COTSprocessors/standard OS in a single ND or a single card within an ND. Incertain embodiments of such a hybrid network device, a platform VM(i.e., a VM that that implements the functionality of thespecial-purpose network device 502) could provide forpara-virtualization to the networking hardware present in the hybridnetwork device 506.

Regardless of the above exemplary implementations of an ND, when asingle one of multiple VNEs implemented by an ND is being considered(e.g., only one of the VNEs is part of a given virtual network) or whereonly a single VNE is currently being implemented by an ND, the shortenedterm network element (NE) is sometimes used to refer to that VNE. Alsoin all of the above exemplary implementations, each of the VNEs (e.g.,VNE(s) 530A-R, VNEs 560A-R, and those in the hybrid network device 506)receives data on the physical NIs (e.g., 516, 546) and forwards thatdata out the appropriate ones of the physical NIs (e.g., 516, 546). Forexample, a VNE implementing IP router functionality forwards IP packetson the basis of some of the IP header information in the IP packet;where IP header information includes source IP address, destination IPaddress, source port, destination port (where “source port” and“destination port” refer herein to protocol ports, as opposed tophysical ports of a ND), transport protocol (e.g., user datagramprotocol (UDP) (RFC 768, 2460, 2675, 4113, and 5405), TransmissionControl Protocol (TCP) (RFC 793 and 1180), and differentiated services(DSCP) values (RFC 2474, 2475, 2597, 2983, 3086, 3140, 3246, 3247, 3260,4594, 5865, 3289, 3290, and 3317).

FIG. 5C illustrates various exemplary ways in which VNEs may be coupledaccording to some embodiments of the invention. FIG. 5C shows VNEs570A.1-570A.P (and optionally VNEs 570A.Q-570A.R) implemented in ND 500Aand VNE 570H.1 in ND 500H. In FIG. 5C, VNEs 570A.1-P are separate fromeach other in the sense that they can receive packets from outside ND500A and forward packets outside of ND 500A; VNE 570A.1 is coupled withVNE 570H.1, and thus they communicate packets between their respectiveNDs; VNE 570A.2-570A.3 may optionally forward packets between themselveswithout forwarding them outside of the ND 500A; and VNE 570A.P mayoptionally be the first in a chain of VNEs that includes VNE 570A.Qfollowed by VNE 570A.R (this is sometimes referred to as dynamic servicechaining, where each of the VNEs in the series of VNEs provides adifferent service—e.g., one or more layer 4-7 network services). WhileFIG. 5C illustrates various exemplary relationships between the VNEs,alternative embodiments may support other relationships (e.g.,more/fewer VNEs, more/fewer dynamic service chains, multiple differentdynamic service chains with some common VNEs and some different VNEs).

The NDs of FIG. 5A, for example, may form part of the Internet or aprivate network; and other electronic devices (not shown; such as enduser devices including workstations, laptops, netbooks, tablets, palmtops, mobile phones, smartphones, multimedia phones, Voice Over InternetProtocol (VOIP) phones, terminals, portable media players, GPS units,wearable devices, gaming systems, set-top boxes, Internet enabledhousehold appliances) may be coupled to the network (directly or throughother networks such as access networks) to communicate over the network(e.g., the Internet or virtual private networks (VPNs) overlaid on(e.g., tunneled through) the Internet) with each other (directly orthrough servers) and/or access content and/or services. Such contentand/or services are typically provided by one or more servers (notshown) belonging to a service/content provider or one or more end userdevices (not shown) participating in a peer-to-peer (P2P) service, andmay include, for example, public webpages (e.g., free content, storefronts, search services), private webpages (e.g., username/passwordaccessed webpages providing email services), and/or corporate networksover VPNs. For instance, end user devices may be coupled (e.g., throughcustomer premise equipment coupled to an access network (wired orwirelessly)) to edge NDs, which are coupled (e.g., through one or morecore NDs) to other edge NDs, which are coupled to electronic devicesacting as servers. However, through compute and storage virtualization,one or more of the electronic devices operating as the NDs in FIG. 5Amay also host one or more such servers (e.g., in the case of the generalpurpose network device 504, one or more of the virtual machines 562A-Rmay operate as servers; the same would be true for the hybrid networkdevice 506; in the case of the special-purpose network device 502, oneor more such servers could also be run on a hypervisor executed by thecompute resource(s) 512); in which case the servers are said to beco-located with the VNEs of that ND.

A virtual network is a logical abstraction of a physical network (suchas that in FIG. 5A) that provides network services (e.g., L2 and/or L3services). A virtual network can be implemented as an overlay network(sometimes referred to as a network virtualization overlay) thatprovides network services (e.g., layer 2 (L2, data link layer) and/orlayer 3 (L3, network layer) services) over an underlay network (e.g., anL3 network, such as an Internet Protocol (IP) network that uses tunnels(e.g., generic routing encapsulation (GRE), layer 2 tunneling protocol(L2TP), IPSec) to create the overlay network).

A network virtualization edge (NVE) sits at the edge of the underlaynetwork and participates in implementing the network virtualization; thenetwork-facing side of the NVE uses the underlay network to tunnelframes to and from other NVEs; the outward-facing side of the NVE sendsand receives data to and from systems outside the network. A virtualnetwork instance (VNI) is a specific instance of a virtual network on aNVE (e.g., a NE/VNE on an ND, a part of a NE/VNE on a ND where thatNE/VNE is divided into multiple VNEs through emulation); one or moreVNIs can be instantiated on an NVE (e.g., as different VNEs on an ND). Avirtual access point (VAP) is a logical connection point on the NVE forconnecting external systems to a virtual network; a VAP can be physicalor virtual ports identified through logical interface identifiers (e.g.,a VLAN ID).

Examples of network services include: 1) an Ethernet LAN emulationservice (an Ethernet-based multipoint service similar to an InternetEngineering Task Force (IETF) Multiprotocol Label Switching (MPLS) orEthernet VPN (EVPN) service) in which external systems areinterconnected across the network by a LAN environment over the underlaynetwork (e.g., an NVE provides separate L2 VNIs (virtual switchinginstances) for different such virtual networks, and L3 (e.g., IP/MPLS)tunneling encapsulation across the underlay network); and 2) avirtualized IP forwarding service (similar to IETF IP VPN (e.g., BorderGateway Protocol (BGP)/MPLS IPVPN RFC 4364) from a service definitionperspective) in which external systems are interconnected across thenetwork by an L3 environment over the underlay network (e.g., an NVEprovides separate L3 VNIs (forwarding and routing instances) fordifferent such virtual networks, and L3 (e.g., IP/MPLS) tunnelingencapsulation across the underlay network)). Network services may alsoinclude quality of service capabilities (e.g., traffic classificationmarking, traffic conditioning and scheduling), security capabilities(e.g., filters to protect customer premises from network—originatedattacks, to avoid malformed route announcements), and managementcapabilities (e.g., full detection and processing).

FIG. 5D illustrates a network with a single network element on each ofthe NDs of FIG. 5A. Specifically, FIG. 5D illustrates network elements(NEs) 570A-H with the same connectivity as the NDs 500A-H of FIG. 5Awith a centralized approach for maintaining reachability and forwardinginformation (also called network control), according to some embodimentsof the invention.

FIG. 5D illustrates that a centralized approach 574 (also known assoftware defined networking (SDN)) that decouples the system that makesdecisions about where traffic is sent from the underlying systems thatforwards traffic to the selected destination. The illustratedcentralized approach 574 has the responsibility for the generation ofreachability and forwarding information in a centralized control plane576 (sometimes referred to as a SDN control module, controller, networkcontroller, OpenFlow controller, SDN controller, control plane node,network virtualization authority, or management control entity), andthus the process of neighbor discovery and topology discovery iscentralized. The centralized control plane 576 has a south boundinterface 582 with a data plane 580 (sometime referred to theinfrastructure layer, network forwarding plane, or forwarding plane(which should not be confused with a ND forwarding plane)) that includesthe NEs 570A-H (sometimes referred to as switches, forwarding elements,data plane elements, or nodes). The centralized control plane 576includes a network controller 578, which includes a centralizedreachability and forwarding information module 579 that determines thereachability within the network and distributes the forwardinginformation to the NEs 570A-H of the data plane 580 over the south boundinterface 582 (which may use the OpenFlow protocol). The centralizedreachability and forwarding information module 579 contains a virtualtable manager (VTM) 124. VTM 124 coordinates with network elements toperform flow table virtualization. For example, VTM 124 may send arequest to a network element to ask the network element to create a setof virtual tables. VTM 124 may store the mapping between the flow tablesand the virtual tables.

The network intelligence is centralized in the centralized control plane576 executing on electronic devices that are typically separate from theNDs. For example, where the special-purpose network device 502 is usedin the data plane 580, each of the control communication andconfiguration module(s) 532A-R of the ND control plane 524 typicallyinclude a control agent that provides the VNE side of the south boundinterface 582. In this case, the ND control plane 524 (the computeresource(s) 512 executing the control communication and configurationmodule(s) 532A-R) performs its responsibility for participating incontrolling how data (e.g., packets) is to be routed (e.g., the next hopfor the data and the outgoing physical NI for that data) through thecontrol agent communicating with the centralized control plane 576 toreceive the forwarding information (and in some cases, the reachabilityinformation) from the centralized reachability and forwardinginformation module 579 (it should be understood that in some embodimentsof the invention, the control communication and configuration module(s)532A-R, in addition to communicating with the centralized control plane576, may also play some role in determining reachability and/orcalculating forwarding information—albeit less so than in the case of adistributed approach; such embodiments are generally considered to fallunder the centralized approach 574, but may also be considered a hybridapproach).

While the above example uses the special-purpose network device 502, thesame centralized approach 574 can be implemented with the generalpurpose network device 504 (e.g., each of the VNE 560A-R performs itsresponsibility for controlling how data (e.g., packets) is to be routed(e.g., the next hop for the data and the outgoing physical NI for thatdata) by communicating with the centralized control plane 576 to receivethe forwarding information (and in some cases, the reachabilityinformation) from the centralized reachability and forwardinginformation module 579; it should be understood that in some embodimentsof the invention, the VNEs 560A-R, in addition to communicating with thecentralized control plane 576, may also play some role in determiningreachability and/or calculating forwarding information—albeit less sothan in the case of a distributed approach) and the hybrid networkdevice 506. In fact, the use of SDN techniques can enhance the NFVtechniques typically used in the general purpose network device 504 orhybrid network device 506 implementations as NFV is able to support SDNby providing an infrastructure upon which the SDN software can be run,and NFV and SDN both aim to make use of commodity server hardware andphysical switches.

FIG. 5D also shows that the centralized control plane 576 has a northbound interface 584 to an application layer 586, in which residesapplication(s) 588. The centralized control plane 576 has the ability toform virtual networks 592 (sometimes referred to as a logical forwardingplane, network services, or overlay networks (with the NEs 570A-H of thedata plane 580 being the underlay network)) for the application(s) 588.Thus, the centralized control plane 576 maintains a global view of allNDs and configured NEs/VNEs, and it maps the virtual networks to theunderlying NDs efficiently (including maintaining these mappings as thephysical network changes either through hardware (ND, link, or NDcomponent) failure, addition, or removal).

While FIG. 5D illustrates the simple case where each of the NDs 500A-Himplements a single NE 570A-H, it should be understood that the networkcontrol approaches described with reference to FIG. 5D also work fornetworks where one or more of the NDs 500A-H implement multiple VNEs(e.g., VNEs 530A-R, VNEs 560A-R, those in the hybrid network device506). Alternatively or in addition, the network controller 578 may alsoemulate the implementation of multiple VNEs in a single ND.Specifically, instead of (or in addition to) implementing multiple VNEsin a single ND, the network controller 578 may present theimplementation of a VNE/NE in a single ND as multiple VNEs in thevirtual networks 592 (all in the same one of the virtual network(s) 592,each in different ones of the virtual network(s) 592, or somecombination). For example, the network controller 578 may cause an ND toimplement a single VNE (a NE) in the underlay network, and thenlogically divide up the resources of that NE within the centralizedcontrol plane 576 to present different VNEs in the virtual network(s)592 (where these different VNEs in the overlay networks are sharing theresources of the single VNE/NE implementation on the ND in the underlaynetwork).

On the other hand, FIGS. 5E and 5F respectively illustrate exemplaryabstractions of NEs and VNEs that the network controller 578 may presentas part of different ones of the virtual networks 592. FIG. 5Eillustrates the simple case of where each of the NDs 500A-H implements asingle NE 570A-H (see FIG. 5D), but the centralized control plane 576has abstracted multiple of the NEs in different NDs (the NEs 570A-C andG-H) into (to represent) a single NE 570I in one of the virtualnetwork(s) 592 of FIG. 5D, according to some embodiments of theinvention. FIG. 5E shows that in this virtual network, the NE 570I iscoupled to NE 570D and 570F, which are both still coupled to NE 570E.

FIG. 5F illustrates a case where multiple VNEs (VNE 570A.1 and VNE570H.1) are implemented on different NDs (ND 500A and ND 500H) and arecoupled to each other, and where the centralized control plane 576 hasabstracted these multiple VNEs such that they appear as a single VNE570T within one of the virtual networks 592 of FIG. 5D, according tosome embodiments of the invention. Thus, the abstraction of a NE or VNEcan span multiple NDs.

While some embodiments of the invention implement the centralizedcontrol plane 576 as a single entity (e.g., a single instance ofsoftware running on a single electronic device), alternative embodimentsmay spread the functionality across multiple entities for redundancyand/or scalability purposes (e.g., multiple instances of softwarerunning on different electronic devices).

Similar to the network device implementations, the electronic device(s)running the centralized control plane 576, and thus the networkcontroller 578 including the centralized reachability and forwardinginformation module 579, may be implemented a variety of ways (e.g., aspecial purpose device, a general-purpose (e.g., COTS) device, or hybriddevice). These electronic device(s) would similarly include computeresource(s), a set or one or more physical NICs, and a non-transitorymachine-readable storage medium having stored thereon the centralizedcontrol plane software.

Standards such as OpenFlow define the protocols used for the messages,as well as a model for processing the packets. The model for processingpackets includes header parsing, packet classification, and makingforwarding decisions. Header parsing describes how to interpret a packetbased upon a well-known set of protocols. Some protocol fields are usedto build a match structure (or key) that will be used in packetclassification (e.g., a first key field could be a source media accesscontrol (MAC) address, and a second key field could be a destination MACaddress).

Packet classification involves executing a lookup in memory to classifythe packet by determining which entry (also referred to as a forwardingtable entry or flow entry) in the forwarding tables best matches thepacket based upon the match structure, or key, of the forwarding tableentries. It is possible that many flows represented in the forwardingtable entries can correspond/match to a packet; in this case the systemis typically configured to determine one forwarding table entry from themany according to a defined scheme (e.g., selecting a first forwardingtable entry that is matched). Forwarding table entries include both aspecific set of match criteria (a set of values or wildcards, or anindication of what portions of a packet should be compared to aparticular value/values/wildcards, as defined by the matchingcapabilities—for specific fields in the packet header, or for some otherpacket content), and a set of one or more actions for the data plane totake on receiving a matching packet. For example, an action may be topush a header onto the packet, for the packet using a particular port,flood the packet, or simply drop the packet. Thus, a forwarding tableentry for IPv4/IPv6 packets with a particular transmission controlprotocol (TCP) destination port could contain an action specifying thatthese packets should be dropped.

Making forwarding decisions and performing actions occurs, based uponthe forwarding table entry identified during packet classification, byexecuting the set of actions identified in the matched forwarding tableentry on the packet.

However, when an unknown packet (for example, a “missed packet” or a“match-miss” as used in OpenFlow parlance) arrives at the data plane580, the packet (or a subset of the packet header and content) istypically forwarded to the centralized control plane 576. Thecentralized control plane 576 will then program forwarding table entriesinto the data plane 580 to accommodate packets belonging to the flow ofthe unknown packet. Once a specific forwarding table entry has beenprogrammed into the data plane 580 by the centralized control plane 576,the next packet with matching credentials will match that forwardingtable entry and take the set of actions associated with that matchedentry.

A network interface (NI) may be physical or virtual; and in the contextof IP, an interface address is an IP address assigned to a NI, be it aphysical NI or virtual NI. A virtual NI may be associated with aphysical NI, with another virtual interface, or stand on its own (e.g.,a loopback interface, a point-to-point protocol interface). A NI(physical or virtual) may be numbered (a NI with an IP address) orunnumbered (a NI without an IP address). A loopback interface (and itsloopback address) is a specific type of virtual NI (and IP address) of aNE/VNE (physical or virtual) often used for management purposes; wheresuch an IP address is referred to as the nodal loopback address. The IPaddress(es) assigned to the NI(s) of a ND are referred to as IPaddresses of that ND; at a more granular level, the IP address(es)assigned to NI(s) assigned to a NE/VNE implemented on a ND can bereferred to as IP addresses of that NE/VNE.

Each VNE (e.g., a virtual router, a virtual bridge (which may act as avirtual switch instance in a Virtual Private LAN Service (VPLS) (RFC4761 and 4762) is typically independently administrable. For example, inthe case of multiple virtual routers, each of the virtual routers mayshare system resources but is separate from the other virtual routersregarding its management domain, AAA (authentication, authorization, andaccounting) name space, IP address, and routing database(s). MultipleVNEs may be employed in an edge ND to provide direct network accessand/or different classes of services for subscribers of service and/orcontent providers.

Within certain NDs, “interfaces” that are independent of physical NIsmay be configured as part of the VNEs to provide higher-layer protocoland service information (e.g., Layer 3 addressing). The subscriberrecords in the AAA server identify, in addition to the other subscriberconfiguration requirements, to which context (e.g., which of theVNEs/NEs) the corresponding subscribers should be bound within the ND.As used herein, a binding forms an association between a physical entity(e.g., physical NI, channel) or a logical entity (e.g., circuit such asa subscriber circuit or logical circuit (a set of one or more subscribercircuits)) and a context's interface over which network protocols (e.g.,routing protocols, bridging protocols) are configured for that context.Subscriber data flows on the physical entity when some higher-layerprotocol interface is configured and associated with that physicalentity.

The operations of the flow diagrams FIGS. 3-4 are described withreference to the exemplary embodiment of FIGS. 1, 2 and 5. However, itshould be understood that the operations of flow diagrams can beperformed by embodiments of the invention other than those discussedwith reference to the exemplary embodiment of FIGS. 1, 2 and 5, and theexemplary embodiment of FIGS. 1, 2 and Scan perform operations differentthan those discussed with reference to the flow diagrams of FIGS. 3-4.

While the flow diagrams in the figures herein above show a particularorder of operations performed by certain embodiments of the invention,it should be understood that such order is exemplary (e.g., alternativeembodiments may perform the operations in a different order, combinecertain operations, overlap certain operations, etc.).

Different embodiments of the invention may be implemented usingdifferent combinations of software, firmware, and/or hardware. Thus, thetechniques shown in the figures can be implemented using code and datastored and executed on one or more electronic devices (e.g., an endsystem, a network device). Such electronic devices store and communicate(internally and/or with other electronic devices over a network) codeand data using computer-readable media, such as non-transitorycomputer-readable storage media (e.g., magnetic disks; optical disks;random access memory; read only memory; flash memory devices;phase-change memory) and transitory computer-readable transmission media(e.g., electrical, optical, acoustical or other form of propagatedsignals—such as carrier waves, infrared signals, digital signals). Inaddition, such electronic devices typically include a set of one or moreprocessors coupled to one or more other components, such as one or morestorage devices (non-transitory machine-readable storage media), userinput/output devices (e.g., a keyboard, a touchscreen, and/or adisplay), and network connections. The coupling of the set of processorsand other components is typically through one or more busses and bridges(also termed as bus controllers). Thus, the storage device of a givenelectronic device typically stores code and/or data for execution on theset of one or more processors of that electronic device.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, can be practiced with modificationand alteration within the spirit and scope of the appended claims. Thedescription is thus to be regarded as illustrative instead of limiting.

What is claimed is:
 1. A method implemented in a network element coupledto a software-defined networking (SDN) system, wherein the SDN systemcontains a set of network elements processing traffic flows and a SDNcontroller managing the set of network elements, the method comprising:creating a set of virtual tables for processing packets of traffic flowsat the network element based on a set of flow tables of the networkelement, wherein the set of flow tables is ordered in a sequence;mapping each of the set of virtual tables to a single flow table of theset of flow tables, wherein the mapping causes at least one flow tablebeing mapped to a plurality of the set of virtual tables; and forwardingpackets of traffic flows to the set of virtual tables for processing. 2.The method of claim 1, wherein the creating the set of virtual tablescomprises: for each virtual table, performing at least one of: setting atable identifier for the virtual table; setting a set of key componentsof the virtual table; setting a set of actions upon receiving a matchingpacket; and setting an entry for match miss.
 3. The method of claim 1,wherein the mapping each of the set of virtual tables to a flow table ofthe network element comprises: mapping a table identifier of a virtualtable to a table identifier of a flow table.
 4. The method of claim 1,wherein the forwarding packets of traffic flows comprises: uponreceiving a packet of a traffic flow at a virtual table, searching for amatching flow entry in a mapping flow table of the virtual table; uponfinding the matching flow entry in the mapping flow table, determining acorresponding set of actions of the matching flow entry for the virtualtable; and performing the corresponding set of actions.
 5. The method ofclaim 4, wherein the searching for the matching flow entry is to matchkey components of the packet to match fields of flow entries in themapping flow table.
 6. The method of claim 4, further comprising: uponfinding no matching flow entry in the mapping flow table, performing aninstruction for match miss.
 7. The method of claim 4, furthercomprising: updating a counter in the virtual table upon the performingthe corresponding set of actions.
 8. The method of claim 1, furthercomprising: identifying the network element with flow tablevirtualization capability through at least one of: capabilitynegotiation between the network element and the SDN controller; adding avendor extension in communication between the network element and theSDN controller; adding a predetermined data path identifier for thenetwork element with flow table virtualization capability; andinitiating communication from the network element through apredetermined port to the SDN controller.
 9. A network element coupledto a software-defined networking (SDN) system, wherein the SDN systemcontains a plurality of network elements processing traffic flows and aSDN controller managing the plurality of network elements, the networkelement comprising: a processor and a non-transitory machine-readablestorage medium coupled to the processor, the non-transitorymachine-readable storage medium containing an virtual table coordinatormodule executable by the processor, wherein the network element isoperative to: create a set of virtual tables for processing packets oftraffic flows at the network element based on a set of flow tables ofthe network element, wherein the set of flow tables is ordered in asequence, map each of the set of virtual tables to a single flow tableof the set of flow tables, wherein the mapping causes at least one flowtable being mapped to a plurality of the set of virtual tables, andforward packets of traffic flows to the set of virtual tables forprocessing.
 10. The network element of claim 9, wherein the creation ofthe set of virtual tables is to: for each virtual table, perform atleast one of: setting a table identifier for the virtual table; settinga set of key components of the virtual table; setting a set ofinstructions upon receiving a matching packet; and setting an entry formatch miss.
 11. The network element of claim 9, wherein the mapping isto: map a table identifier of a virtual table to a table identifier of aflow table.
 12. The network element of claim 9, wherein the forwardingis to: upon receiving a packet of a traffic flow at a virtual table,search for a matching flow entry in a mapping flow table of the virtualtable; upon finding the matching flow entry in the mapping flow table,determine a corresponding set of actions of the matching flow entry forthe virtual table; and perform the corresponding set of actions.
 13. Anon-transitory machine-readable medium having instructions storedtherein, which when executed by a processor, cause the processor toperform operations in a network element coupled to a software-definednetworking (SDN) system, wherein the SDN system contains a set ofnetwork elements processing traffic flows and a SDN controller managingthe set of network elements, the operations comprising: creating a setof virtual tables for processing packets of traffic flows at the networkelement based on a set of flow tables of the network element, whereinthe set of flow tables is ordered in a sequence; mapping each of the setof virtual tables to a single flow table of the set of flow tables,wherein the mapping causes at least one flow table being mapped to aplurality of the set of virtual tables; and forwarding packets oftraffic flows to the set of virtual tables for processing.
 14. Thenon-transitory machine-readable medium of claim 13, wherein the creatingthe set of virtual tables comprises: for each virtual table, performingat least one of: setting a table identifier for the virtual table;setting a set of key components of the virtual table; setting a set ofactions upon receiving a matching packet; and setting an entry for matchmiss.
 15. The non-transitory machine-readable medium of claim 13,wherein the mapping each of the set of virtual tables to a flow table ofthe network element comprises: mapping a table identifier of a virtualtable to a table identifier of a flow table.
 16. The non-transitorymachine-readable medium of claim 13, wherein the forwarding packets oftraffic flows comprises: upon receiving a packet of a traffic flow at avirtual table, searching for a matching flow entry in a mapping flowtable of the virtual table; upon finding the matching flow entry in themapping flow table, determining a corresponding set of actions of thematching flow entry for the virtual table; and performing thecorresponding set of actions.
 17. The method of claim 16, wherein thesearching for the matching flow entry is to match key components of thepacket to match fields of matching flow entries in the mapping flowtable.
 18. The method of claim 16, further comprising: upon finding nomatching flow entry in the mapping flow table, performing an instructionfor match miss.
 19. The method of claim 16, further comprising: updatinga counter in the virtual table upon the performing the corresponding setof actions.
 20. The method of claim 13, further comprising: identifyingthe network element with flow table virtualization capability through atleast one of: capability negotiation between the network element and theSDN controller; adding a vendor extension in communication between thenetwork element and the SDN controller; adding a predetermined data pathidentifier for the network element with flow table virtualizationcapability; and initiating communication from the network elementthrough a predetermined port to the SDN controller.